This invention relates to drive belts, and in particular to drive belts for use in a linear motion cable drive mechanism in which a plurality of drive belts are helically wrapped around a driven element. An example of such a cable drive mechanism is shown in U.S. Pat. No. 4,274,574. Such mechanisms employ a plurality of drive assemblies, each including a set of pulleys and a drive belt, to advance an elongated driven element along its longitudinal axis. Each of the drive belts is wrapped helically about the driven element such that simultaneous rotation of the assemblies and lengthwise movement of the drive belts causes advancement of the driven element without rotation thereof.
The path travelled by drive belts in such systems causes the belts to undergo a variety of stresses. Fleet angle fluctuations, small pulley radii, and substantial twisting of the drive belts are examples of factors which contribute to difficulties in belt design.
A characteristic of cable drive systems which utilize helically disposed belts is that as tension in the belts increases, there is a tendency for the belts to straighten, and for the driven element to disengage itself from contact with the drive belts. It is desirable to maintain even spacing of the drive belts about the driven element. Furthermore, because variations in diameter in the driven element, there is a need to balance circumferential forces between the belts.
Drive belts made in accordance with the present invention satisfy the above requirements, and a preferred embodiment of the invention comprises a continuous loop of water resistant material with at least one encapsulated strength member inside. The belt has two resilient legs which abut legs of adjacent belts to insure even spacing of a plurality of belts when the belts are helically wrapped around a driven element. A belt of the present invention may have a generally W-shaped cross section.
These and other aspects of the invention will be better understood after a reading the following specification in conjunction with the accompanying drawings.